Stress distribution across laterally heterogeneous laboratory fault gouge layers
Abstract
In recent decades, many developments have been made in understanding the spatial heterogeneity of large-displacement tectonic fault zones and how it relates to the mechanical response of the fault. Zones of fault creep often surround patches of little or no fault slip that may periodically slip in seismogenic events. In nature, large/mature faults can extend for tens to hundreds of kilometers and intersect many different lithologies. Thus the fault gouges that comprise the fault core can have significant spatial variation along the strike of the fault producing mechanical heterogeneity. Understanding how stress builds up during the inter-seismic period across regions with different mechanical properties is of paramount importance for elucidating processes involved with earthquake nucleation. We present experimental results where heterogeneous faults are simulated in the laboratory by placing gouges of different composition adjacent to each other in different geometric arrangements using a direct shear arrangement. During shearing, arrays of high-resolution strain gauges are used to track how the stress builds up across the different gouge patches positioned at different points along the fault. Gouges with different frictional properties are used to test how the bulk and local strength evolves when frictionally 'weak' (e.g. clay) materials are deformed next to materials with much greater friction coefficients (e.g. quartz). The results show that significant stress heterogeneities develop across the different patches and also within individual patches of the same material. These results could have important implications for earthquake nucleation on large seismogenic faults.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMMR31A..08B
- Keywords:
-
- 3902 Creep and deformation;
- MINERAL PHYSICS;
- 8010 Fractures and faults;
- STRUCTURAL GEOLOGY;
- 8034 Rheology and friction of fault zones;
- STRUCTURAL GEOLOGY;
- 8045 Role of fluids;
- STRUCTURAL GEOLOGY